International agreements require reduction in the stockpiles of conventional and nuclear munitions. There is therefore a great incentive to destroy and/or reclaim explosives, propellants, and pyrotechnic material efficiently and without significant environmental impact.
Procedures conventionally used to demilitarize conventional munitions include incineration of reclaimed explosives and open burning or detonation. However, many areas of the United States no longer permit open burning and detonation of large quantities of high-energy compositions; increasingly, constraints are placed even on the uncontrolled destruction of small quantities of these substances.
Federal and state environmental legislation to limit, control and remove pollutants entering the environment have resulted in a great many programs dealing with disposal of propellants and explosives. Pollutants resulting from disposal and clean-up of explosives and propellants must be reduced as much as possible. Moreover, explosives and propellants cannot be landfilled because of their energetic nature. Radioactive materials, many of which may be compounded with explosives or propellants, cannot be disposed of by open burning or detonation.
Although propellants and explosives can contain a great variety of different materials, there are some classes of materials that are conventionally used and must be disposed of in an environmentally safe way. For example, the propellant and explosive compounds themselves, such as nitrate esters, are generally dangerous, may be toxic, and cannot be landfilled or subjected to open burning. Oxides of nitrogen resulting from burning these compounds are regulated air pollutants which are toxic and irritating; these nitrogen oxides corrosively react with ozone photochemically to produce smog. Water-soluble nitrates in the propellants and explosives are toxic compounds which contribute to eutrophication of water systems.
Historically, many of these components of explosives and propellants have been removed from the environment using special-purpose incinerators which include gas scrubbers and solid particle collectors. These include flashing furnaces that remove all traces of explosive from metal parts to assure safety in handling; fluidized-bed incinerators that burn slurries of ground up propellants or explosives in oil; and rotary kilns to destroy explosive and contaminated waste and bulk explosives.
Procedures that have been suggested for decomposing explosives and propellants include fluidized-bed incineration, composting, and biodenitrification. Soluble components have been extracted with organic solvents. However, using organic solvents presents problems in disposing of the solvents used.
Chemical Abstracts No. 98:203821, discloses the results of an assessment of dry humus sediments contaminated with TNT. However, this is merely an assessment of the contents of the mixture, rather than an attempt to treat the TNT.
Chemical Abstracts No. 103:1222284, discloses the results of an investigation as to whether humus from a clear-cut coniferous forest could support nitrate reduction. This study found that ammonium was immobilized but not nitrified. No nitrate was assimilated or reduced to ammonium.
British patent specification 191,741 discloses a method for recovering ammonia from ammonia-containing gases by bringing the gas into contact with crude carbonaceous bodies such as soft lignite or peat. The carbonaceous material absorbs ammonia, which can then be used as a fertilizer. This method is limited to treating ammoniacal gases.
Musselman, U.S. Pat. No. 3,987,237, discloses a process for disposing of pyrotechnic flares comprised of magnesium sodium nitrate and a binder. The flare is crushed and soaked in a solvent to dissolve the binder material, and the dissolved binder is decanted. The remaining magnesium and sodium nitrate are washed in water to dissolve the sodium nitrate, which is recovered for use as a fertilizer. The remaining magnesium is dried for reuse as an ingredient in a pyrotechnic device. There is no indication that the nitrogen values can be recovered from the sodium nitrate.
Production of munitions-grade nitrocellulose causes a significant problem with respect to disposing of the waste "fines" inevitably discharged from the manufacturing operations. These waste solids are remarkably stable, and to date have been treated by alkaline hydrolysis. After alkaline hydrolysis, a nitrogen mass balance could not be achieved, and a substantial fraction of the nitrate-nitrogen remains bound after digestion to an unknown organic compound(s), as noted in Nitrocellulose Fines Separation and Treatment, Workshop Proceedings, School of Civil Engineering, Purdue University, West Lafayette, Ind., 4-5 Nov., 1993.